Plastic Flow Of Material Research Articles

Effect of material positioning on Si-rich TIG welded joints of AA6082 and AA8011 by friction stir processing

The TIG-welded specimens were friction stir processed (FSPed) to analyze the impact material positioning of the base metals AA8011 and AA6082. The tests included the energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction, microstructure, hardness, tensile test and fracture surface analysis. The mean grain size of 24.83 µm was obtained for the TIG welded joint, 8.68 µm for the FSPed joint with AA6082 alloy on the advancing side (A.S), while 11.14 µm was obtained when the AA8011 was positioned on the A.S. In the TIG + FSPed zone, an intricate vortex flow pattern could be seen. The extremely superplastic flow of plasticized material is seen in the mixed flow zone, which results in a tumultuous intercalation pattern. In situ extrusions of different alloys and severe plastic, deformation was induced by stirring tool action. Lamellae structure was generated by moving the plasticized material layer by layer. In this zone, vigorous mixing and penetration of A6082 and AA8011 were observed. The maximum tensile strength and strain rate of the TIG weldment showed a significant increase after friction stir processing from 83.83 MPa with a strain rate of 23.79% to 90.09 MPa with a tensile strain of 28.04. However, evaluating the FSPed joints, the AA8011-AA6082 specimen had better tensile properties. Moreover, the fracture surface analysis correlated with the tensile tests. The FSPed AA6082-AA8011 joint showed a higher hardness than the AA8011-AA6082 one.

An Analysis of Practices and Challenges for Plastic Recycling Industry in Malaysia

There is a significant increase in plastic consumption with the growing economies of Asia, causing severe environmental issues as a large proportion of the plastic waste is not appropriately disposed due to the underdeveloped collection systems. The situation in Malaysia is particularly worrying as the total plastic waste increased by nearly 30% in 2018, becoming the second-highest of the entire household solid waste. This problem can be addressed by improving the plastic waste management system and increasing the plastic wastes recycling rate. Therefore, this study aims to investigate the current situation of plastic waste generation. Malaysia’s waste management framework is a unique integration of the formal and informal sectors. The lack of uniformity has been the main challenge for the policy implementation in improving plastic waste management. From the plastic material flow analysis, only 41.4% of the plastic wastes were recycled in 2019. The most recycled plastic types in Malaysia are high-density polyethylene (HDPE), polyethylene terephthalate (PET), low-density polyethylene (LDPE), and polypropylene (PP), as they are easier to collect and have higher density. From the identified plastic recycling process flow, the main challenge is low recyclability. Most recyclables are usually contaminated with food waste or non-recyclable plastic, which hinders the sorting process. Informing the public how to recycle plastic waste properly can increase the effectiveness of recyclables collection as well as the sorting process.

Visualization of plastic flow in metal ultrasonic welding by adding interlayer

The plastic flow of ultrasonic welding joints is a significant factor in getting high bonding strength joints. In this paper, a method of adding a kind of material different from the base metal as interlayers are used to reveal the plastic flow of materials at the interface. The results indicate that this method can clearly show the plastic flow in joints with different parameters. It is found that swirl zones appear in the joints with higher parameters. Fine equiaxed grains appear in the zone with large deformation. And it is observed that the grains in the joint have an obvious orientation by EBSD maps. Two models of interfacial plastic flow were proposed according to the microstructural and grain orientation observation of joints under different parameters.

Wear Performance of Circular Shim against Cam in Engine Bench Test.

Unlike the conventional engine, the valve train of a certain type of engine uses a circular shim instead of a tappet to wear against the cam. To verify the reliability of the shim, an engine bench test was used to test its wear performance. The total duration of the bench test was 1000 h, which was divided into three stages. In each stage, the test equipment was stopped, and the shims were disassembled to observe the surface morphology during the worn process. Precious long-term data were obtained. With the extension of the bench test time, weight loss increased. The maximum weight loss occurs 1000 h after worn, which is about twice that of 350 h. During the wear process, a plastic flow of material was found on the subsurface, and fatigue wear marks occurred on the surface. With an increase in test time, the wear marks increased, leading to material spalling and the formation of pits. The wear mechanism was the mixed wear of fatigue wear and adhesive wear.

Discerning the circularity of the plastic industry in Bangladesh through the lens of material flow analysis

This study performs the first national plastic material flow analysis (MFA) of Bangladesh to obtain essential information for developing the roadmap for circular economy. It quantified plastic flows for the fiscal year (FY) 2019–2020 by circumventing data deficiencies through innovative methodical approach and an improvised coupling of primary data from extensive field surveys and historical foreign trade statistics. In FY2019–2020, Bangladesh exported only 22 % of its total annual plastic import of 1,710,296 metric tons. The packaging sector consumed the highest 937,242 metric tons (48 % of the domestic consumption). Per capita consumption and waste generation were 10.13 kg and 7.9 kg, respectively, leading to plastic use intensity of 7.94 g per 2010US$ GDP in FY2019–2020, indicating an active materialization phase and growth. Bangladesh recycled 362,332 metric tons of plastic a year, 90 % of which was done by the country's robust informal sector, leading to a better recycling efficiency (28 %) compared to developed countries. Bangladesh also fared better in plastic decoupling, with a decoupling factor of 21 compared to the average of 13 for its developed counterparts. Scenario-based forecast indicated a maximum of nearly 6 million metric tons of potential imports in FY2029–2030 for the business-as-usual scenario. The plastic industry exhibited better performance than many countries despite poor institutional capacity and lack of policy support by leveraging the informal and semi-formal sectors. Policy insights particularly on improving waste management by the informal sector, community awareness and stakeholder engagement, improving manufacturing processes and technologies may significantly contribute to circularizing plastic use in Bangladesh to achieve SDG12 targets.

Numerical simulation for the comparison of thermal and plastic material flow behavior between symmetrical and asymmetrical boundary conditions during friction stir welding

Numerical simulation for the comparison of thermal and plastic material flow behavior between symmetrical and asymmetrical boundary conditions during friction stir welding

Experiment and simulation of SiC particle-reinforced aluminum matrix composites fabricated by friction stir processing

The influence of the pre-implanted reinforced particles on the temperature field and the flow field of the processed zone directly determines the microstructure and properties of the aluminum matrix composites fabricated by friction stir processing (FSP). However, the differences in the characteristics of processed materials, especially the effect of pre-implanted reinforced particles on the flow of plastic materials, have rarely been reported. In this study, the temperature distribution of the processed zone was obtained by experimental measurement and numerical simulation. The model of the effect of the SiC particles as reinforced particles on the temperature field and the flow field of the processed zone was established. The influence of the SiC particles on the flow of plastic materials during the FSP was further investigated. The refinement, particle size, and distribution of the SiC particles in the processed zone of the FSPed multi-pass composites were also discussed in detail. The microhardness of the processed zone was also tested and discussed. The results showed that the temperature field at the contact interface between the SiC particles and the matrix in the processed zone was not continuously distributed. Due to the collision and hindrance of the reinforced SiC particles, the flow direction of plastic materials in the processed zone had been changed many times during the flow process. The initial average particle sizes of the SiC particles have a significant effect on the flow path of the processed plastic material. The microhardness of the processed zone of the FSPed specimens is significantly higher than that of the matrix.

Revealing the bonding mechanisms between deposit and substrate of the friction rolling additive manufactured hybrid aluminum alloys

Friction rolling additive manufacturing (FRAM) is an emerging solid-state additive manufacturing technology for high-strength aluminum alloys that are prone to produce solidification defects using fusion-based additive manufacturing method. However, the mechanisms responsible for good bonding between the FRAM interlayers remain unclear. This study successfully reveals such mechanisms for FRAM-produced hybrid AA2319 and AA6061 aluminum alloys using 3D X-ray computed tomography, electron backscatter diffraction, and transmission electron microscopy. Three findings concerning the quality of bonding between adjacent layers in FRAM were obtained. Firstly, material plastic flow and macroscopic migration behavior occurred simultaneously along the longitudinal and transverse directions at the interlayer, forming a macroscopic mechanically interlocking nonplanar interface. The convex thread at the tool head increased the material flow in the transverse direction, facilitating material mixing in the adjacent layer. Secondly, severe plastic deformation resulted in significant grain refinement on both sides of the interface. The average grain size reduction rates for the sides of AA2319 and AA6061 were 98.3% and 95.9%, respectively. Thirdly, direct contact with no obvious oxides resulted in complete metallurgical interface bonding. These findings can aid in the elucidation of the basic physical process of FRAM and provide guidance for process parameter optimization and tool head design in the future. • Mechanically interlocked non-planar interface was formed during the FRAM process. • Material flow occurred simultaneously along with the longitudinal and transverse directions at the interlayer. • Thread protrusion significantly increased the material flow in the transverse direction. • Severe plastic deformation resulted in significant grain size reduction for both sides of the interface. • It was experimentally proved that direct contact with no oxide was achieved at the interface, forming a complete metallurgical bonding.

Influence of forging action on the microstructural and mechanical characteristics of the friction stir welded joints of aluminum alloy with varied joint configurations

The variation in the forging action during single-side friction stir welding (SS-FSW) and double side friction stir welding (DS-FSW) joining of AA-6061 T6 alloy by friction stir welding (FSW) process was conducted. The microscopic study of the stir zone (SZ) of SS-FSW joint configurations showed that the forging action obtained with a 3° tool tilt angle (TTA) provided better intermixing of material, with significant downward and inclined flow of plasticized material under the shoulder interaction zones. This led to the maximum grain refinement as compared to the forging action obtained with 0° and 2° TTA. For DS-FSW joint, a good interlocking between the material stirred during the first and second pass was observed, which led to maximum joint efficiency, and the elimination of the problem of insufficient root penetration observed during the SS-FSW. The misorientation analysis revealed that the percentage of high angle grain boundaries (HAGBs) significantly increased for DS-FSW joint due to the small thermal gradient along the plate thickness. Moreover, the dominance of B/[Formula: see text] shear texture with sufficient dissimilarity in the crystallographic orientation to the random texture was observed within the SZ of DS-FSW joint.

2D FEM simulation and experimental verification of Al 7075‐T6 during turning process

AbstractIn this work, temperature distribution, effective stress and strain distribution in Al 7075‐T6 material and plastic flow of materials during turning process have been studied using Deform 3D v11.0 software. The four different points (P1, P2, P3, and P4) were chosen at the different locations in the cylindrical workpiece and the graph has been plotted with different parameters namely, temperature distribution, effective stress and strain. For temperature distribution, a good agreement has been found between simulation and experimental results at P4. The following results obtained from the simulation: In tertiary zone, the maximum temperature of specimen reaches upto 142 °C at points P1 due to friction between the tool rack face and the lower surface of chip. Maximum effective stress value reaches upto 650 MPa and 704 MPa at P1 and P4 respectively in the first sticking zone due to the combined effect of high normal force by tool edge and ploughing force. The effective strain value at P1 and P4 obtained, strain at P4 reaches maximum compare to P1 due to friction and unven temperature distribution. Additionally, chip analysis has been performed with microscopic image.

Erosion wear resistance mechanism of erosion ripples

Erosion ripples widely exist on natural and industrial surfaces suffering gas–solid flow erosion. During the steady state of erosion ripples formation, the material removal and plastic flow rate of the material basically reach a dynamic equilibrium. In this state, the erosion rate of the surface material is steady and at a low level. In this paper, the relationship between erosion ripples and the erosion characteristics of surface materials was explored by experimental and simulation methods. Under the conditions of air pressures of 0.3, 0.4 and 0.5 MPa and erosion angles of 30°, 40° and 50°, several erosion ripples were prepared on the surface of 1060 aluminium alloy samples by sandblasting. According to the obtained morphological parameters and orthogonal test design, rippled samples with rectangular, triangular and semicircular groove sections were designed. The effect of morphology parameters on the erosion resistance of the sample was analysed by a sandblasting test. The results showed that the rippled samples have lower erosion rates than the plate sample. The cross-sectional shape of grooves is the most obviously affected factor. The velocity distribution and surface pressure distribution on the surface of rippled and plate samples were analysed by FLUENT software, and the results showed that the low-speed reflow vortex will be formed in grooves of erosion ripples that can change the near-wall flow field conditions. The differential pressure generated on two sides of the ridge between adjacent grooves, as well as the area decrease of erosion caused by the “shaded effect,” may be the cause of the erosion resistance. The results of this study can provide new insight into the active erosive wear resistance method of mechanical components.

The Influence of Tool Shape on Plastic Metal Flow, Microstructure and Properties of Friction Stir Welded 2024 Aluminum Alloy Joints

In this paper, the effect of different shapes of tool pin on the plastic flow of 2024-T6 aluminum alloy during friction stir welding was studied. In order to observe the plastic flow of materials more clearly, we chose the method of friction stir welding of dissimilar materials, considering the different corrosive characteristics of aluminum alloys made of different materials when exposed to the same corrosive liquid. By studying and comparing the temperature field, macro and microstructure, microhardness and tensile properties of welded joints, the results indicated that the metal in the weld nugget zone (WNZ) mainly came from the base metal of the advancing side, the thread being the driving force of the downward movement of the FSW plastic metal. The deep groove thread tool pin had the strongest ability to drive the metal downward. The conical cam thread tool pin had the strongest stirring effect on materials and the best metal fluidity. The macroscopic morphology, microstructure, mechanical properties and fracture morphology of different joints were analyzed, and the results showed that all joints could form an excellent union, with an onion ring pattern appearing in cross-section. The minimum grain size of the WNZ formed by the conical cam thread stirring head was 7~12 μm; the hardness was least at the junction of the heat affected zone (HAZ) and the thermo-mechanically affected zone (TMAZ). However, the hardness of the weld formed by the conical cam thread at this point was higher than that of other stirring heads; the tensile strength of all joints was more than 80% of the BM, and the maximum tensile strength of the joint welded by the conical cam thread tool pin was 364.27 MPa, accounting for 86.73% of the base metal (BM). The elongation after break was 14.95%. Tensile fracture morphology analysis showed that all joints were fractured by plastic fracture.

Importance of Finite Element Analysis for Verification of Technological Parameters of Seamless Tubes Production Obtained by Experiment

Experimental research on the process of cold tubes drawing was performed in order to obtain important information about the behaviour of the tube material in the drawing tool during the drawing to the required outer diameter of Ø12 mm. The DEFORM-3D simulation software was an important tool for verifying the plastic flow of material in the drawing tool (i.e. drawing die), as well as for optimizing the technological parameters of cold tubes drawing. In the finite element (FE) analysis, emphasis was placed on determining the influence of tool geometry, strain degree, drawing speed and friction on the size of the drawing force and the quality of production of drawn tubes. The paper points out the importance of simulation software for common comparison of results obtained from laboratory experiment and FE analysis of the process of tubes drawing. By comparing the results, the reliability of the used simulation software was proved, as the results were identical for all monitored technological parameters. Computer simulation brings valuable knowledge that is important for the correct design of the drawing tool as well as for the technology of production of tubes with precise dimensions.

Study on the edge defects of high volume fraction 70% SiCp/Al composites in ultrasonic-assisted milling

Directing at the hard machinability of high volume fraction 70% SiCp/Al composites, a longitudinal and torsional ultrasonic-assisted milling (LTUAM) method is proposed to improve the edge quality and machining efficiency. By observing the metallographic structure of the material, a three-dimensional (3D) finite element model of random distribution of spherical, elliptical and polygonal SiC particles is established and analyzed by ABAQUS simulation software. The formation mechanism of edge defects, stress distribution, defect characteristics and the effect of machining parameters on milling forces are investigated during ultrasonic-assisted milling. The results show that the edge defects appear at the inlet, outlet and middle edge position, especially is more serious at the outlet position. The SiC particles failure modes mainly include particle pullout, particle shearing, and crushing, moreover, the edge defects mainly include matrix tearing, edge breakage, burrs, bulges and pits. Ultrasonic-assisted milling (UAM) with a certain range of ultrasonic amplitude could effectively reduce the surface fragmentation rate and milling force, and it not only could slow down the expansion of cracks, but also increase the plastic flow of material, and obtain better edge quality compared with the traditional machining method. Comparing the results of finite element analysis and experimental tests, it shows that the simulation results are in good agreement with that of tests.

Microstructural investigation along the transverse section of the lower gauge corner flow lips formed in high rails of mild curves

The microstructure of the ‘flow lip’ formed at the lower gauge face in high rails in curved tracks has been investigated along the transverse section. The rails served in tracks having radii of curvature of 1500 m(S1) and 2000 m(S2) respectively. Optical images reveal the formation of an outermost white etching layer (WEL) followed by a brown etching layer (BEL) and deformed sublayers. Cracks originated from the WEL regions and from the notches at the extreme end of the flow lip. The cracks originate from the WEL region due to exhaustion of ductility, whereas, at the extreme end of the flow lip the cracks originate due to stress concentration caused by the notches generated due to uneven plastic flow of material. Using SEM (scanning electron microscopy) and EBSD (electron back-scattered diffraction), the WEL region is identified to consist of fine grains of ferrite and particles/fine fragments of cementite. The cementite in the WEL region is present as particles in S1 and as broken fragments as well as particles in S2. From the SEM images, the BEL has a similar appearance to WEL but with intermittent patches of lamellae-type features. The lamellae type features are much larger in S2 than S1 implying that the radius of curvature can significantly affect the level of deformation. The deformation was lower in S2 than S1 for similar distances from the outer edge, possibly due to less severe shear loading in a less sharply curved rail.

Thermal process and material flow during dissimilar double-sided friction stir spot welding of AZ31/ZK60 magnesium alloys

A computational fluid dynamics (CFD) model for double-sided friction stir spot welding (FSSW) between AZ31 and ZK60 magnesium alloys using adjustable pins is proposed in this paper. Multiple phase flow theories are combined to track the metal interface and phase distribution using FLUENT software. The heat transfer and material flow for the 5 stages of the friction stir welding process, including the pre-heating, plunging, welding, rising and post-heating stages, are presented. For further evaluation, the calculated flow and thermal responses are compared with experimental data, which overall showed good agreement. The material between the upper and lower pins is softened after the pre-heating process and is then driven by the plunging pin to form a keyhole below the upper tool and a bulge region in the bottom of the plates. The welding interface between the pins is bowl-shaped after plunging, and grows uneven during the welding stage due to the extensive plastic material flow. The keyhole is then fully eliminated after the rising of the pins. After welding, the region between the tools is heated to a maximum temperature of 670 K and the welding interface slightly fluctuates and a phase mixing phenomenon occurs, suggesting that AZ31 and ZK60 plates are well joined by using the adjustable pins.

Effect of reinforcement size hybridization on the wear properties of SiCp/Cu Composites

Abstract Reinforcement size is an important factor that influences the mechanical and tribological properties of particulate reinforced metal matrix composites (PRMMCs). However, relatively few works have been carried out to investigate this issue. There are still many problems to be solved, on the optimum design of PRMMCs of tribological applications. In this work, copper-matrix composites reinforced with SiC particles of mono-size and hybrid-size are fabricated through a powder-metallurgy plus hot-extrusion method. The main purpose is to investigate the effect of reinforcement size hybridization on the dry sliding wear behavior of PRMMCs. The results indicate that finer particles result in a better reinforcing effect and significantly reduce the plastic flow and adhesive transfer of surface and subsurface material. The deeply embedded coarse particles bear the external applied load and resist the plowing effect of the counterpart. The different roles of the particulate components with various sizes promote the exertion of the other’s strengthening function, therefore resulting in higher wear resistance.

Process Relationship in High-Stress Friction Coupled with Complex Shaped Counterbody and Friction Stir Welding Al-Mg-Sc-Zr Alloy

Model research tests of plastic deformation, fragmentation and flow of aluminum alloy material of Al-Mg-Sc-Zr system under high loaded friction in pair with a steel counterbody of a complex shape and comparison of the obtained result with the structure formed by friction stir welding have been carried out. The conducted studies show that the structure formed by extrusion of the material from the friction zone and its compaction in the channel of the counterbody is, in general, close in structure to the structure formed by friction stir welding of similar material. The distinguishing features of the structure formed in the model experiments on friction include the introduction into the stirring zone of material with deformed large-crystal structure, increased grain size of the stirring zone, the presence of defects and differences in the geometry of the stirring zone.

Correlation of heterogeneous interface microstructure and mechanical performance of inertia friction welded 6061 Al alloy joint

The non-uniformity of microstructure and property at the interface of the inertia friction welded 6061Al alloy with a grain size of 5 μm was addressed in the present study. The grain became finer from the centre interface region (∼1.1 μm) to the outer interface region (0.8–0.9 μm) due to the enhanced material plastic flow. The textures at different characteristic interfacial regions evolved from different routes: {111}<110> and {001}<110> textures were generated at the centre interface with base metal texture disappeared under the shear effect of friction pressure. Apart from {100}<001> and {210}<001> base metal textures, new textures of {310}<130> and (315)<130> appeared at the outer 1/2R and edge interface regions arising from the rotation of grains. With the enhancements of temperature and material plastic flow, the fraction of precipitates increased from the centre to edge interface, all being higher than that in BM, while the dislocation density showed an opposite trend. The well-predicted microhardness model showed although the Hall–Petch strength mechanism was enhanced from 620 MPa to 650 MPa from centre to edge due to refined grains, the lesser contributions from solid solution and dislocation (390 MPa reduced to 270 MPa) were responsible for the continuously decreased hardness. Microtensile tests also revealed a decreasing trend of local bonding strength from the centre (270 MPa) to the edge interface (230 MPa) with different sizes of dimples observed.

The mechanism of the anomalous behavior of the plastic flow of materials with high crystal relief caused by the dynamic impurity subsystem

A model of dynamic interaction of dislocations with an impurity subsystem of crystals with a high potential relief of the crystal lattice (Peierls barriers) is developed. Such materials include metals with body-centered cubic structure, semiconductors, ceramics, and many others. It is shown that the modification of impurity migration barriers near the dislocation core significantly affects the segregation of impurities on the moving dislocation. The presence of a substantially nonequilibrium initial stage of segregation kinetics leading to anomalies of dislocation dynamics and yield strength of materials is substantiated. Keywords: dislocation dynamics, segregation of impurities in the dislocation core, synergetics of dislocation and impurity subsystems, stable and unstable regimes, plastic flow anomalies.